In general, there are several methods for making a color filter used for a color liquid crystal display apparatus such as dyeing, dispersion, electrodeposition, and printing. These techniques for making a color filter are roughly divided into the following two groups: one uses dye and the other uses pigment as an agent for coloring. The dyeing and pigmentation mechanisms for coloring are similar to each other, however, both methods are very different from each other in that dye is dissolved in a fabricating process for a color filter and is present in the order of molecules in the color filter, while pigment disperses as particles of about 0.1 micron since the pigment is not dissolved into the solvent.
A color filter including pigments has many advantages, however, some kinds of pigments degrade polarization of light and thereby cause a problem of significantly degrading the display contrast ratio as discussed in "A Color Filter for 512-Color Displaying 10.4" Sized TFT-LCD" of, Proceedings of the 7th Joint Conference on Color Technology, Color Engineering Conference Papers 5.2 on the Seventh International Symposium Associated Four Optical Societies, 1990. This problem is thought to be caused by scattering, double birefregence, etc., however, this problem has not yet been quantitatively explained. In spite of the lack of quantitative explanation, providing a high contrast display is a significant problem which should be solved. Moreover, the use of dyes in color filters is difficult because of the lack of stability of the dye in the color filter. Therefore, if a color filter can be developed which has color stability and small depolarization, this would be very advantageous to the contrast of display.